Using Two X-Ray Images to Create a Parameterized Scoliotic Spine Model and Analyze Disk Stress Adjacent to Spinal...

Area of Science:

• Spine biomechanics
• Medical imaging
• Finite element analysis

Background:

• Posterior instrumentation is a standard treatment for severe adolescent idiopathic scoliosis (AIS).
• Adjacent segment degeneration (ASD) is a known complication following spinal fusion surgery for AIS.
• Limited research exists on the biomechanical impact of AIS surgery on adjacent spinal segments, and methods for creating patient-specific finite element (FE) models reflecting vertebral deformation are needed.

Purpose of the Study:

• To develop a case-specific, parameterized FE model using biplanar X-ray images to simulate vertebral deformation in AIS.
• To compare pre- and postoperative biomechanical changes in adjacent segments, including range of motion (ROM), endplate stress, and intervertebral disk stress, using FE analysis.

Main Methods:

• A patient-specific FE model of the spine was created from biplanar X-ray images of an AIS patient using ANSYS software.
• The preoperative model's accuracy was validated against CT reconstruction, with minor differences in Cobb angle and kyphosis measurements.
• A flexion moment was applied to simulate spinal loading, comparing pre- and postoperative models to assess biomechanical parameters.

Main Results:

• A validated, case-specific FE model reflecting coronal plane vertebral deformation was successfully developed from X-ray data.
• Biomechanical analysis revealed a decrease in maximum endplate and intervertebral disk stress in the cranial adjacent segment.
• Conversely, the caudal adjacent segment experienced an increase in stress after simulated surgical instrumentation.

Conclusions:

• The developed FE modeling approach provides a method for analyzing biomechanical effects on spinal segments adjacent to instrumentation in AIS.
• Surgical instrumentation for AIS alters the biomechanical environment of adjacent segments, leading to stress redistribution.
• Further research using this FE modeling technique can help understand and potentially mitigate adjacent segment degeneration post-surgery.